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Various stressors factor such as changing diet, transport, diseases influence
the balance of natural microbial flora in the gastrointestinal tract. Under
these conditions, the use of antibiotics is inevitable in order to control or
eliminate harmful microorganisms. Continuous and long-term use of
antibiotics to prevent or control disease in livestock and poultry feed may
lead to the presence of these compounds in the products [1,2]. Since 1997,
the World Health Organization (WHO) and the Food and Agriculture
Organization (FAO) have paid much attention to the potential risks of the
addition of antibiotics stimulating growth to livestock and poultry diets
and finally the use of growth-promoting antibiotics in Europe was banned
in 2006 [3].

The short chain fatty acids (SCFA) are considered as the potential
alternative to antibiotic growth promoter [4]. Acetic acid is one such
SCFA, which has higher bactericidal activity when the acid is undissociated.
The bacterial cell takes up un-dissociated fatty acid, which, by
ionizing fatty acid inside the bacterial cell, there is a change in the
intracellular pH leading to the death of bacterial [5]. Organic acids added
to feed for their various beneficial effects on gut function and micro flora,
feed preservation from microbial invasion, inhibition of pathogenic
bacteria, enhancing mineral absorption, and improvement of nutrient
digestibility [6].

Acetic acid also appears to play a role in the development of the intestinal
epithelium. It is reported that acetate derived from the fermentation of non-starch polysaccharides is considered to be important for normal
development of epithelial cells [7]. Adding organic acids to food or
drinking water reduces the pH of the digestive system, the accumulation of
pathogens in the intestinal wall, stimulates the development of beneficial
intestinal microbial flora [8], helping to overcome the beneficial bacterial
population to pathogenic bacteria and the reduction of toxic metabolites
that produced by harmful bacteria [9].

Apple vinegar is one of the apple products that contain various types of
flavonoids including quercetin, camproforol, catechins, apicotin,
anthocyanin, cyanidin-3-glucoside and organic acids such as acetic acid
and malic acid. Apple vinegar has antibiotic, antibacterial and antifungal
properties. Beta-carotene available in apple vinegar has antioxidant
properties. Consumption apple vinegar improves the immune systems as
well as help to maintain the blood acid-base balance [10].

The newly studies by author and his contributors [11,12] revealed that
broiler chickens drinking water supplemented with vinegar improves feed
efficiency during 1-10 days of age. No effects of drinker water
supplemented with vinegar on relative weights of lymphoid organs, and
meat yields found. Drinking water supplemented with vinegar
significantly increased villus height (VH), crypt depth (CD) and decreased
small intestine muscular thickness (MT) measured at 42 days of age.
Another important finding of the present studied was the reduction in
carcass abdominal fat content by drinking water supplementation of
vinegar. Finally organic acid might be promising alternatives for to
eliminate antibiotic in broiler chicken production.

Acknowledgement

We greatly appreciate the financial support of this research from vice
president in research at the Ferdowsi University of Mashhad, Iran.